1. Field of the Invention
The present invention relates to a method and a carrier element for producing an electronic component, particularly a sensor for use in a motor vehicle.
2. Description of Related Art
The known concepts in the packaging of sensors use design approaches that are becoming ever smaller and are fully integrated for implementing the function. Housing concepts for “packaging” sensor chips, e.g. “land grid arrays” integrate all the components of a circuit into a tiny encasing (mold compound), which includes only a few cubic millimeters. Such miniaturized circuits represent an enormous challenge for “second-level packaging”, that is, the further processing to form a sensor having opportunities for fastening and plug connectors.
Since such miniaturized circuits, as for instance LGA's, no longer require any printed circuit board or other circuit substrates, these are typically mounted directly in surrounding sensor housings. As an approach in this instance, one may use the 2-component injection molding method, in which the LGA housing, that is connected using a metallic carrier strip, is first extrusion-coated with a relatively soft material, such as silicone, in a first step, and, in an additional step, this construct is, in turn, extrusion-coated with a housing plastic in an injection molding method. This sequence is necessary because the pressures, required in the plastic injection molding of several 100 bar, would damage the LGA housing in such a way that at least the durable function of the circuit is not assured. However, even the previous extrusion-coating, using a damping material such as silicone, represents some danger: As, for instance, the displacement of the silicone material when the plastic mass comes down on one side or, for example, the penetration of the silicone, because of the high pressure that is present during the plastic injecting, into the electrical contact location between the LGA housing and the metallic carrier element. Consequently, the use of a purely mechanical terminal connection for the electronic contact is questionable, and one has to get around it by going to materially integral connections such as soldering connections. Because of current RoHS Regulations (EG-Regulation 2002/95/EG on the restriction of the use of certain hazardous substances in electrical units and electronic units) the latter must not contain any lead and, because of the content of required flux in the solder, they represent a not inconsiderable risk of the contamination and carrying over of flux into the silicone mass during the first injection molding process. In addition, at soldering locations without lead, there is created the problem of whisker formation.